IgG TORCH

The IgG TORCH Test is a blood test that screens for a group of infections commonly referred to as the TORCH infections. The acronym TORCH stands for Toxoplasmosis, Other infections (such as Syphilis, Varicella-Zoster), Rubella, Cytomegalovirus (CMV), and Herpes Simplex Virus (HSV). These infections can pose serious health risks, particularly for pregnant women and their unborn babies. The IgG version of the test detects IgG antibodies, which indicate past infection and immune system response to these infections. The IgG TORCH Test is widely used in Dubai, especially for pregnant women, to ensure the health and safety of both the mother and the child.

2. Purpose / Clinical Significance

• Pregnancy Screening: The IgG TORCH Test is crucial for screening pregnant women for infections that can affect the fetus, potentially causing birth defects, developmental delays, or miscarriage.

• Assessing Immunity: The test helps to determine whether a person has previously been exposed to any of the TORCH infections, which can indicate immunity or susceptibility to re-infection.

• Identifying Past Infections: By measuring IgG antibodies, the test identifies past exposure to infections like rubella, toxoplasmosis, and cytomegalovirus that may not cause symptoms but can still be dangerous during pregnancy.

• Assessing Risk of Congenital Infections: The IgG TORCH Test helps in identifying infections that can be transmitted from the mother to the baby during pregnancy, potentially leading to congenital diseases.

• Guiding Healthcare Decisions: For pregnant women or women planning pregnancy, knowing the results of the test can help healthcare providers recommend preventive measures, vaccines, or additional screenings.

3. Principle
The IgG TORCH Test works by detecting IgG antibodies specific to each of the TORCH infections in the blood.

• IgG antibodies are produced by the immune system after a person has been exposed to an infection. A positive result for IgG indicates a past infection, and the person is likely immune to the infection.

• Each TORCH infection is tested separately, and the presence of IgG antibodies for each infection is recorded.

• If IgG antibodies are detected for an infection, it means that the person has likely had a previous exposure to the infection and is immune to it. A negative result indicates no prior exposure, and the person may be susceptible to the infection.

4. Specimen Requirements

• Sample Type: The test requires a blood sample.

• Collection Method: Blood is typically drawn from a vein in the arm using a syringe (venipuncture).

• Volume: A small amount of blood (approximately 3-5 ml) is sufficient for the test.

• Preparation: No special preparation is required, but it is important to inform the healthcare provider about any ongoing medications or health conditions. For pregnant women, testing is typically done during the first trimester or as advised by the doctor.

5. Common Methods

• Enzyme-Linked Immunosorbent Assay (ELISA): The most commonly used method for detecting IgG antibodies against the TORCH infections. ELISA uses specific antigens from each infection to bind with the antibodies in the patient’s blood, producing a measurable response.

• Indirect Fluorescent Antibody (IFA) Test: Another method used to detect IgG antibodies, where the sample is incubated with fluorescent-labeled antigens, making it easier to observe the antibody presence under a microscope.

• Western Blotting: A more advanced method for confirming specific antibodies after initial testing through ELISA or IFA.

6. Interpretation of Results

• Positive IgG: A positive result for IgG antibodies indicates past exposure to the infection and possible immunity.

  • For Toxoplasmosis: A positive IgG result means the person has had a prior infection and is immune.

  • For Rubella: A positive IgG indicates immunity, which is important for pregnant women, as rubella infection during pregnancy can cause birth defects.

  • For Cytomegalovirus (CMV): A positive IgG means the person has had a prior infection, and in most cases, it does not pose a risk unless reactivation occurs during pregnancy.

  • For Herpes Simplex: A positive IgG result means the person has been previously infected, though it does not indicate active infection.

• Negative IgG: A negative result indicates no past exposure to the infection, and the person may not have immunity. This could mean they are at risk for future infection, and preventive measures or vaccinations may be necessary.

7. Reference Range
The reference range for IgG antibodies varies based on the infection being tested. In general:

• Toxoplasmosis IgG: Positive if > 1.0 IU/mL

• Rubella IgG: Positive if > 10 IU/mL

• Cytomegalovirus IgG: Positive if > 1.0 IU/mL

• Herpes Simplex IgG: Positive if > 1.0 IU/mL

• Other infections (like Syphilis, Varicella-Zoster): Specific values vary and depend on the pathogen and laboratory methods used.

8. Follow-up Testing

• Further Testing for Active Infection: If an IgG TORCH test shows negative results or if there is a concern for an active infection (for instance, if a woman is pregnant and has no IgG antibodies for rubella), additional tests such as IgM antibodies may be required to determine whether a recent or current infection is present.

• Ultrasound for Fetal Health: For pregnant women, if a TORCH infection is suspected or confirmed, additional monitoring with ultrasound or other imaging techniques may be performed to assess the health of the fetus and detect any congenital abnormalities.

• Vaccinations: Women who are not immune to infections like rubella may need vaccinations before pregnancy or during the pregnancy planning phase.

The IgG TORCH Test is a crucial blood test that helps detect past exposure to a range of infections, including toxoplasmosis, rubella, cytomegalovirus (CMV), and herpes simplex, all of which can pose significant risks during pregnancy. For women in Dubai, this test provides an essential screening tool to ensure both maternal and fetal health. By identifying past infections and immunity levels, the IgG TORCH Test plays a critical role in preventing the transmission of these infections to the baby during pregnancy.